2 files changed, 15 insertions, 3 deletions
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index bc34692702..c7c8e00f40 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -589,8 +589,13 @@ static void ComputeDATE_TIME(SourceLocation &DATELoc, SourceLocation &TIMELoc,
 /// specified by the identifier as a standard language feature.
 static bool HasFeature(const Preprocessor &PP, const IdentifierInfo *II) {
   const LangOptions &LangOpts = PP.getLangOptions();
+  StringRef Feature = II->getName();
 
-  return llvm::StringSwitch<bool>(II->getName())
+  // Normalize the feature name, __foo__ becomes foo.
+  if (Feature.startswith("__") && Feature.endswith("__") && Feature.size() >= 4)
+    Feature = Feature.substr(2, Feature.size() - 4);
+
+  return llvm::StringSwitch<bool>(Feature)
            .Case("address_sanitizer", LangOpts.AddressSanitizer)
            .Case("attribute_analyzer_noreturn", true)
            .Case("attribute_availability", true)
@@ -724,10 +729,16 @@ static bool HasExtension(const Preprocessor &PP, const IdentifierInfo *II) {
     return false;
 
   const LangOptions &LangOpts = PP.getLangOptions();
+  StringRef Extension = II->getName();
+
+  // Normalize the extension name, __foo__ becomes foo.
+  if (Extension.startswith("__") && Extension.endswith("__") &&
+      Extension.size() >= 4)
+    Extension = Extension.substr(2, Extension.size() - 4);
 
   // Because we inherit the feature list from HasFeature, this string switch
   // must be less restrictive than HasFeature's.
-  return llvm::StringSwitch<bool>(II->getName())
+  return llvm::StringSwitch<bool>(Extension)
            // C11 features supported by other languages as extensions.
            .Case("c_alignas", true)
            .Case("c_atomic", true)
diff --git a/lib/Sema/AttributeList.cpp b/lib/Sema/AttributeList.cpp
index a3791dedf7..9b74fc03ce 100644
--- a/lib/Sema/AttributeList.cpp
+++ b/lib/Sema/AttributeList.cpp
@@ -101,7 +101,8 @@ AttributeList::Kind AttributeList::getKind(const IdentifierInfo *Name) {
   StringRef AttrName = Name->getName();
 
   // Normalize the attribute name, __foo__ becomes foo.
-  if (AttrName.startswith("__") && AttrName.endswith("__"))
+  if (AttrName.startswith("__") && AttrName.endswith("__") &&
+      AttrName.size() >= 4)
     AttrName = AttrName.substr(2, AttrName.size() - 4);
 
   return llvm::StringSwitch<AttributeList::Kind>(AttrName)